1. Field of the Invention
The invention provides nucleotide sequences from Coryneform bacteria coding for the Dep33 protein and a process for the fermentative preparation of amino acids using bacteria in which the dep33 efflux protein is attenuated.
2. Discussion of the Background
L-amino acids, in particular L-lysine, are used in human medicine and in the pharmaceutical industry, in the foodstuffs industry and very particularly in animal nutrition.
It is known that amino acids can be prepared by the fermentation of strains of coryneform bacteria, in particular Corynebacterium glutamicum. Due to the importance of this area, constant efforts are made to improve the method of preparation. Process improvements may relate to fermentation technology measures such as, for example, stirring and supplying with oxygen, or the composition of the nutrient media such as, for example, the sugar concentration during fermentation, or working up to the product form by, for example, ion exchange chromatography, or the intrinsic performance properties of the microorganism itself.
Methods of mutagenesis and selection are used to improve the output properties of these microorganisms. Strains that are resistant to antimetabolites or are auxotrophic for regulatory significant metabolites and which produce amino acids can be obtained with these methods.
Methods of recombinant DNA engineering have also been used for improving Corynebacterium strains ability to produce L-amino acid by amplifying individual amino acid biosynthesis genes and examining the effects on amino acid production.
However, there remains a critical need for improved methods of producing L-amino acids and thus for the provision of strains of bacteria producing higher amounts of L-amino acids. On a commercial or industrial scale even small improvements in the yield of L-amino acids, or the efficiency of their production, are economically significant. Prior to the present invention, it was not recognized that attenuation of the dep33 gene encoding the efflux protein Dep33 would improve L-amino acid yields.